1. Field of the Invention
The present invention relates to a hydrogen supplying device for a fuel cell which supplies hydrogen, as a fuel, to a fuel cell. In particular, the present invention relates to a hydrogen supplying device for a fuel cell provided with a hydrogen occlusion tank containing a hydrogen occlusion alloy and a hydrogen tank in which hydrogen may be stored in a compressed state.
2. Description of the Related Art
As a hydrogen supplying device which supplies hydrogen to a fuel cell mounted on a movable object, such as a vehicle, one which supplies hydrogen discharged from a hydrogen occlusion alloy, in which hydrogen has been occluded, to a fuel cell, has been known as disclosed in, for example, Japanese Unexamined Patent Application, First Publication No. 2000-88196.
When hydrogen is occluded in or discharged from the hydrogen occlusion alloys, heat is associated with the process. That is, it is necessary to remove heat from the hydrogen occlusion alloy when occluding hydrogen, and to supply heat to the hydrogen occlusion alloy when discharging hydrogen. Since the quantity of heat required for discharging hydrogen is supplied from the heat capacity of the hydrogen occlusion alloy, the temperature of the hydrogen occlusion alloy decreases, if no heat is externally supplied, when hydrogen is discharged.
Accordingly, the above-mentioned type hydrogen supplying devices are provided with a heating means for applying heat to the hydrogen occlusion alloy so that hydrogen may be stably discharged from the hydrogen occlusion alloy. The heating means recovers heat which is generated when power is generated by a fuel cell, and utilizes this waste heat as a heating source. At this time, a liquid, such as water, or a gas, such as air, is used as a heating medium.
In the conventional hydrogen supplying device for a fuel cell, however, the quantity of heat, which can be supplied by the heating means, may be insufficient, depending on the conditions under which the fuel cell is operated, for the quantity of heat required by the hydrogen occlusion alloy, even if the hydrogen supplying device is provided with the above-mentioned heating device. For this reason, in some cases, the temperature of the hydrogen occlusion alloy decreases during an operation, and it becomes difficult to supply the required amount of hydrogen to the fuel cell from the hydrogen occlusion alloy.
Accordingly, it is an object of the present invention to provide a hydrogen supplying device for a fuel cell provided with a hydrogen occlusion tank containing a hydrogen occlusion alloy and a hydrogen tank in which hydrogen is stored in a compressed state, which is capable of always stably supplying an amount of hydrogen required by the fuel cell by controlling an amount of hydrogen supplied from the hydrogen occlusion tank and from the hydrogen tank.
In order to solve the above problems, the first aspect of the present invention is a hydrogen supplying device for a fuel cell including: a hydrogen occlusion tank (for example, the hydrogen occlusion tank 1 used in the first through third embodiments which will be described later) in which a hydrogen occlusion alloy is contained, the hydrogen occlusion alloy being capable of occluding and discharging hydrogen which is used as a fuel for a fuel cell (for example, the fuel cell 7 used in the first through third embodiments which will be described later); a hydrogen tank (for example, the hydrogen tank 19 used in the first through third embodiments which will be described later) in which hydrogen to be supplied to the fuel cell can be stored in a compressed state; a heating unit (for example, the duct 3, the junction duct 21, outside air duct 23, the cold air duct 25, the heat exchange tube 5, and the flow rate controlling valves V4, V5, and V6 used in the first through third embodiments which will be described later) which supplies heat to the hydrogen occlusion tank; a hydrogen supply line (for example, the hydrogen supply lines 9, 11, 13, and 17 used in the first through third embodiments which will be described later) through which a flow of hydrogen supplied from the hydrogen occlusion tank and a flow of hydrogen supplied from the hydrogen tank can be merged to be supplied to the fuel cell; and a flow rate controlling device (for example, the flow rate controlling valves V1, V2, and V3 used in the first through third embodiments which will be described later) which controls a flow rate of hydrogen supplied from the hydrogen occlusion tank and/or a flow rate of hydrogen supplied from the hydrogen tank.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to supply hydrogen to the fuel cell only from the hydrogen occlusion tank while applying heat to the hydrogen occlusion tank by controlling the flow rate of hydrogen by the flow rate controlling device. Also, it becomes possible to supply hydrogen to the fuel cell only from the hydrogen tank, or from both the hydrogen occlusion tank and the hydrogen tank by merging the flow of hydrogen from the two. Accordingly, the flow rate of hydrogen may be controlled taking into account the heating state of hydrogen occlusion tank by the heating unit.
According to the second aspect of the present invention, in accordance with the first aspect of the invention, the flow rate controlling device controls the flow rate of hydrogen supplied from the hydrogen occlusion tank and/or the flow rate of hydrogen supplied from the hydrogen tank depending on the temperature of the hydrogen occlusion tank.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the flow rate of hydrogen discharged from the hydrogen occlusion tank and the flow rate of hydrogen discharged from the hydrogen tank to be most suitable depending on the temperature of the hydrogen occlusion tank. Accordingly, it becomes possible to stably supply hydrogen to the fuel cell.
According to the third aspect of the present invention, in accordance with the second aspect of the invention, a supply of hydrogen to the fuel cell from the hydrogen occlusion tank is stopped and hydrogen is supplied to the fuel cell only from the hydrogen tank when the temperature of the hydrogen occlusion tank is lower than a lower limit temperature (for example, the lower limit value t1 in the first through third embodiments which will be described later), and hydrogen is supplied to the fuel cell from the hydrogen occlusion tank when the temperature of the hydrogen occlusion tank is equal to or higher than the lower limit temperature.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to supply hydrogen to the fuel cell from the hydrogen tank when the temperature of the hydrogen occlusion tank is lower than the lower limit temperature at which the amount of hydrogen discharged from the hydrogen occlusion tank is decreased. Accordingly, a supply of hydrogen to the fuel cell may be performed in a stable manner even when the supply from the hydrogen occlusion tank is difficult.
According to the fourth aspect of the present invention, in accordance with the second aspect of the invention, a supply of hydrogen to the fuel cell from the hydrogen is stopped and hydrogen is supplied to the fuel cell only from the hydrogen occlusion tank when the temperature of the hydrogen occlusion tank is higher than an upper limit temperature (for example, the upper limit value t2 in the first or third embodiment which will be described later).
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, the amount of hydrogen discharged from the hydrogen occlusion tank is increased and it becomes possible to prevent an increase in the temperature of the hydrogen occlusion tank. Accordingly, an increase in the pressure in the hydrogen occlusion tank may also be prevented.
According to the fifth aspect of the present invention, in accordance with the second aspect of the invention, the flow rate controlling device is controlled depending on a rate of change in the temperature (for example, the rate of change in temperature dT/dt in the first or third embodiments which will be described later) of the hydrogen occlusion tank when the temperature of the hydrogen occlusion tank is equal to or higher than a lower limit temperature (for example, the lower limit value t1 in the first through third embodiments which will be described later) and is equal to or lower than a higher limit temperature (for example, the lower limit value t2 in the first or third embodiment which will be described later).
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the flow rate ratio of the flow rate of hydrogen discharged from the hydrogen occlusion tank to the flow rate of hydrogen discharged from the hydrogen tank to be most suitable depending on the rate of change in the temperature of the hydrogen occlusion tank. Accordingly, the temperature of the hydrogen occlusion tank may be controlled to be a desirable temperature.
According to the sixth aspect of the present invention, in accordance with the fifth aspect of the invention, the flow rate controlling device is controlled so that a supply of hydrogen to the fuel cell from the hydrogen tank is stopped and hydrogen is supplied to the fuel cell only from the hydrogen occlusion tank when the rate of change in the temperature of the hydrogen occlusion tank is increasing, and the flow rate controlling device is controlled so that hydrogen is supplied to the fuel cell from both the hydrogen occlusion tank and the hydrogen tank when the rate of change in the temperature of the hydrogen occlusion tank is decreasing.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to prevent an increase and a decrease in the temperature of the hydrogen occlusion tank while maintaining a stable supply of hydrogen to the fuel cell. Accordingly, both the stable supply of hydrogen to the fuel cell and the proper control of the temperature of the hydrogen occlusion tank may be realized at the same time.
According to the seventh aspect of the present invention, in accordance with the first aspect of the invention, the flow rate controlling device is controlled depending on the rate of change in the temperature (for example, the rate of change in temperature dT/dt in the first through third embodiments which will be described later) of the hydrogen occlusion tank.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the flow rate of hydrogen discharged from the hydrogen occlusion tank and from the hydrogen tank to be most suitable in accordance with the rate of change in the temperature of the hydrogen occlusion tank. Accordingly, the temperature of the hydrogen occlusion tank may quickly reach a desired temperature.
According to the eighth aspect of the present invention, in accordance with the seventh aspect of the invention, the flow rate controlling device controls so that the rate of change in temperature of the hydrogen occlusion tank becomes substantially zero (i.e., dT/dt=0 as in the third embodiment which will be described later).
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the temperature of the hydrogen occlusion tank to be a constant temperature.
According to the ninth aspect of the present invention, in accordance with the first aspect of the invention, the flow rate controlling device is controlled depending on the temperature of the hydrogen occlusion tank and the rate of change in the temperature of the hydrogen occlusion tank.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the flow rate of hydrogen discharged from the hydrogen occlusion tank and from the hydrogen tank to be most suitable depending on the temperature of the hydrogen occlusion tank and the rate of change in the temperature of the hydrogen occlusion tank. Accordingly, it becomes possible to supply hydrogen to the fuel cell in a stable manner while controlling the temperature of the hydrogen occlusion tank to be a desired temperature.
According to the tenth embodiment of the present invention, a hydrogen supplying device for a fuel cell is provided which includes a hydrogen occlusion tank (for example, the hydrogen occlusion tank 1 used in the third embodiment which will be described later) in which a hydrogen occlusion alloy is contained, the hydrogen occlusion alloy being capable of occluding and discharging hydrogen which is used as a fuel for a fuel cell (for example, the fuel cell 7 used in the third embodiment which will be described later); a hydrogen tank (for example, the hydrogen tank 19 used in the third embodiment which will be described later) in which hydrogen to be supplied to the fuel cell can be stored in a compressed state; a heating unit (for example, the duct 3, the junction duct 21, outside air duct 23, the cold air duct 25, the heat exchange tube 5, and the flow rate controlling valves V4, V5, and V6 used in the third embodiment which will be described later) which supplies heat to the hydrogen occlusion tank; a hydrogen supply line (for example, the hydrogen supply lines 9, 11, 13, and 17 used in the first through third embodiments which will be described later) through which a flow of hydrogen supplied from the hydrogen occlusion tank and a flow of hydrogen supplied from the hydrogen tank can be merged to be supplied to the fuel cell; and a flow rate controlling device (for example, the flow rate controlling valve V3 used in the third embodiment which will be described later) which controls a flow rate of hydrogen supplied from the hydrogen tank depending on a flow rate of hydrogen supplied from the hydrogen occlusion tank, the flow rate of hydrogen from the hydrogen occlusion tank being controlled by heat supplied from the heating unit.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to control the amount of hydrogen discharged from the hydrogen tank to be most suitable depending on the amount of hydrogen discharged from the hydrogen occlusion tank.
According to the eleventh aspect of the present invention, in accordance with the tenth aspect of the invention, the flow rate controlling device controls the flow rate of hydrogen supplied from the hydrogen tank so that the total of the flow rate of hydrogen supplied from the hydrogen occlusion tank and the flow rate of hydrogen supplied from the hydrogen tank becomes a flow rate of hydrogen required by the fuel cell.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to supply hydrogen to the fuel cell without excess or deficiency.
According to the twelfth aspect of the present invention, in accordance with the eleventh aspect of the invention, the hydrogen supplying device for a fuel cell further includes a quantity of heat calculation unit (for example, step S317 in the third embodiment which will be described later) which calculates a quantity of heat for heating the hydrogen occlusion tank by the heating unit; and a maximum discharging amount of hydrogen calculation unit (for example, step S325 in the third embodiment which will be described later) which calculates a maximum amount of hydrogen that can be supplied from the hydrogen occlusion tank, based on the quantity of heat for heating the hydrogen occlusion tank calculated by the quantity of heat calculation unit, wherein the flow rate controlling device controls the flow rate of hydrogen supplied from the hydrogen tank depending on the maximum discharging amount of hydrogen calculated by the maximum discharging amount of hydrogen calculation unit.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, since the maximum discharging amount of hydrogen is discharged from the hydrogen occlusion tank, it becomes possible to control the temperature of the hydrogen occlusion tank so as not to be changed and to supply an amount of hydrogen required by the fuel cell.
According to the thirteenth aspect of the present invention, in accordance with the twelfth aspect of the invention, the flow rate controlling device controls so that hydrogen is not supplied from the hydrogen tank if the maximum discharging amount of hydrogen calculated by the maximum discharging amount of hydrogen calculation unit is sufficient for the flow rate of hydrogen required by the fuel cell.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to decrease the consumption of hydrogen in the hydrogen tank, and hence the capacity or the size of the hydrogen tank may be decreased.
According to the fourteenth aspect of the present invention, a hydrogen supplying device for a fuel cell is provided which includes a hydrogen occlusion tank (for example, the hydrogen occlusion tank 1 used in the first or third embodiment which will be described later) in which a hydrogen occlusion alloy is contained, the hydrogen occlusion alloy being capable of occluding and discharging hydrogen which is used as a fuel for the fuel cell; a heating unit (for example, the duct 3, the junction duct 21, the outside air duct 23, the cold air duct 25, the heat exchange tube 5, and the flow rate controlling valves V4, V5, and V6 used in the first or third embodiment which will be described later) which is used for heating the hydrogen occlusion tank by supplying a heating medium (for example, air used in the first or third embodiment which will be described later) which has been heated by using a waste heat from the fuel cell and whose temperature is controllable, to the hydrogen occlusion tank; and a required quantity of heat calculation unit (for example, step S108 or S308 in the first or third embodiment which will be described later) which calculates a quantity of heat required by the hydrogen occlusion tank based on an amount of hydrogen supplied from the hydrogen occlusion tank, wherein the heating unit is controlled depending on the required quantity of heat calculated by the required quantity of heat calculation unit.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to securely supply a required quantity of heat to the hydrogen occlusion tank from the heating unit. Accordingly, the temperature of the hydrogen occlusion tank may be properly controlled, and hydrogen may be stably discharged from the hydrogen occlusion tank.
According to the fifteenth aspect of the present invention, in accordance with the fourteenth aspect of the invention, the hydrogen supplying device for a fuel cell further includes a target temperature calculation unit (for example, step S111, S121, S311, and S321 in the first or third embodiment which will be described later) which calculates a target temperature of the heating medium based on the temperature of the hydrogen occlusion tank, wherein the heating unit is controlled so that the temperature of the heating medium reaches the target temperature.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, it becomes possible to securely control the temperature of the hydrogen occlusion tank to be a desired temperature. Accordingly, the amount of hydrogen supplied to the fuel cell from the hydrogen occlusion tank may be properly controlled.
According to the sixteenth aspect of the present invention, in accordance with the fifteenth aspect of the invention, the target temperature of the heating medium is corrected based on a quantity of heat required by the heating unit for heating the hydrogen occlusion tank and the required quantity of heat calculated by the required quantity of heat calculation unit.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, since the target temperature of the heating medium is corrected based on the quantity of heat required by the heating unit and the calculated required quantity of heat, it becomes possible to quickly and accurately control the temperature of the heating medium. Accordingly, hydrogen may be supplied to the fuel cell from the hydrogen occlusion tank in a stable manner.
According to the seventeenth aspect of the present invention, in accordance with the sixteenth aspect of the invention, the rate of change in the temperature of the hydrogen occlusion tank is calculated based on the quantity of heat required by the heating unit and the required quantity of heat calculated by the required quantity of heat calculation unit, and a target temperature is corrected to be higher than the target temperature calculated by the target temperature calculation unit if the rate of change in the temperature of the hydrogen occlusion tank is decreasing, and a target temperature is corrected to be lower than the target temperature calculated by the target temperature calculation unit if the rate of change in the temperature of the hydrogen occlusion tank is increasing.
According to the hydrogen supplying device for a fuel cell having the above mentioned configuration, since the target temperature of the heating medium is corrected to be higher when the temperature of the hydrogen occlusion tank is decreasing, and to be lower when the temperature of the hydrogen occlusion tank is increasing, it becomes possible to estimate the change in the temperature of the hydrogen occlusion tank and to quickly attain the target temperature of the heating medium so that the temperature of the hydrogen occlusion tank may be controlled to be a desired temperature.